The present invention relates to a key top plate which is preferably applied to a push-button switch used in a variety of electronic devices and also to a method of manufacturing the key top plate.
Heretofore, such a key top plate has been developed in order to make it smaller and thinner that comprises a film plate made of resin film and a key top of mold-resin molded on the film plate. In particular, a specific type of key top plate has been developed that further comprises a print layer including graphic form or the like printed on an under surface of a transparent key top, wherein the print layer is illuminated by an illumination means arranged beneath the layer.
FIG. 5 is a schematic sectional view illustrating a principal part of such a conventional key top plate 300 including one of the key tops 311 thereof. It is to be noted that the actual key top plate 300 includes a lot of key tops 311. The key top plate 300 shown in FIG. 5 has been configured in such a way that a predetermined portion of a film plate 301 made of flexible transparent resin film is pressed upwardly to form a recessed portion 303, the key top 311 made of transparent mold-resin is molded within this recessed portion 303, and then a print layer 313 including desired character, graphic form or symbol is indicatively formed on a flat under surface of the key top 311.
When the key top plate 300 is illuminated from an under side thereof by an illumination means, though not shown, color and/or character of the print layer 313 attached onto the under surface of the key top 311 can be displayed clearly on a top surface side of the key top 311 so as to give a high-class appearance to the key top 311.
In the above conventional example, if, for example, the character or the like is to be printed on a solid print for background in the form of single-color print over a sheet in order to further enhance the high-class appearance, the solid print and the print of the character or the like have been provided in a double-layer as placing one on the other in the section defined as the print layer 313.
However, since the background and the character or the like are both formed on the same plane when the character or the like is printed directly over the solid print for the background, the character would not look as embossed or as if floating above the ground, resulting in failure to provide the enhanced high-class appearance.
Besides, in the above example of the prior art, since the key top 311 is simply attached on the under surface of the recessed portion 303 of the film plate 301, there is still a fear that the key top 311 may be detached from the film plate 301 in case of bad adhesion.
On the other hand, there has been an alternative case where the print layer is formed in the location of the recessed portion 303 of the film plate 301, instead of the print layer 313 being formed on the under surface of the key top 311. In this case, the screen printing method has been typically used as a means for printing this print layer.
However, the conventional screen printing method has imposed a limitation on color scheme. In other words, reproducing a peculiar color tone (e.g., a metallic color tone or a pastel color tone) is difficult and, for example, a photo-image like printing represented by many different colors with fine texture has been difficult.
On the other hand, another type of key top having a different configuration has also been proposed, in which a print layer including a desired coloring is arranged on the top surface of the key top so as to decorate it. Furthermore, an area without a print layer is arranged in a central portion of the print layer so as to allow the inside of the transparent key top to be seen though, thereby improving the aesthetic appearance in design. In addition, in the key top of such configuration, the one that can be manufactured in a simple manner with low cost has been desired.